Where’s Tom? His mother ______ him now.

Who’s that boy reading in the study ? Is it David?—It __________ be David. I saw him go home just now.

Look! The wind is blowing strongly.—Yes, we should keep all the windows and doors ___.

Later，I realized that I didn’t know his name or the least bit about him，________intend to ask．

We should make____a rule for us that the last to leave the classroom shall turn the light off.